The present invention relates to vacuum processing apparatuses and, more particularly, to a vacuum processing apparatus, which applies a film deposition process or the like to an object to be processed such as a semiconductor wafer under a vacuum.
There are plasma CVD (chemical vapor deposition) apparatuses for processing a semiconductor wafer (hereinafter referred to as xe2x80x9cwaferxe2x80x9d). Conventionally, a parallel plate type CVD apparatus is known as such kind of apparatus. In the parallel plate type CVD apparatus, a wafer placement stage constituting a lower electrode is positioned in the center of a vacuum chamber, and a gas supply part constituting an upper electrode is provided so as to face the placement stage. Plasma is generated by applying a voltage between the upper electrode and the lower electrode and the generated plasma is irradiated to the wafer so as to form a predetermined thin film on the wafer. The in-surface uniformity of the thin film formed on the wafer is greatly affected by an isotropy of the exhaust from the vacuum chamber. Accordingly, the exhaust port is provided directly under the placement stage so as to achieve the isotropy of the exhaust.
On the other hand, there is a technical demand for the plasma CVD apparatus to improve a gap fill characteristic. In order to improve the gap fill characteristic, a large flow and high-vacuum process is needed, which cannot be achieved by a conventional apparatus. The reason for this is explained with reference to FIG. 1.
The plasma CVD apparatus shown in FIG. 1 comprises: a cylindrical vacuum chamber 11, a generally circular placement stage 12 that constitutes a lower electrode; a support part 14 for the placement stage 12; a gas supply part 13 that constitutes an upper electrode; an exhaust port 15; and a turbo-molecular pump 16. The semiconductor wafer W as an object to be processed is placed on the placement stage 12.
In recent years, a diameter of the placement stage 12 increases as a diameter of the semiconductor wafer increases. Accordingly, the placement stage 12 having a diameter equal to or larger than the diameter of the exhaust port 15 exists directly above the exhaust port 15. That is, when viewed from above the gas supply part 13, the exhaust port 15 is in a state in which the entire exhaust port 15 is covered by the placement stage 12. In such a structure, particles such as molecules of a gas moving within the vacuum chamber 11 cannot reach the exhaust port 15 by moving along a straight line. Thus, there is a problem in that exhaust efficiency is lowered.
It is a general object of the present invention to provide an improved and useful vacuum processing apparatus in which the above-mentioned problem is eliminated.
A more specific object of the present invention is to provide a vacuum processing apparatus which can achieve high exhaust efficiency and a high ultimate vacuum even for an object to be processed having a large diameter.
In order to achieve the above-mentioned objects, there is provided according to one aspect of the present invention a vacuum processing apparatus for applying a predetermined process to an object to be processed which is placed on a substantially circular placement stage provided in a vacuum chamber by supplying a process gas to the vacuum chamber, characterized in that: the vacuum chamber has a substantially circular exhaust port under the placement stage, the exhaust port having a diameter equal to or smaller than a diameter of the placement stage; and a center axis of the exhaust port (9) is displaced from a center axis of the placement stage.
According to the present invention, since a part of the exhaust port protrudes from the placement stage when viewed from above the placement stage, a high-exhaust rate is achieved, and the ultimate vacuum is increased.
The vacuum processing apparatus according to the present invention may be provided with a support part so as to support the placement stage by extending from a side wall of the vacuum chamber toward the center of the vacuum chamber; and a direction of displacement of the center axis of the exhaust port with respect to the center axis of said placement stage is a direction opposite to an extending direction of the support part.
Since an area underneath the support part of the placement stage is covered by the support part, there is less effect of improvement in the exhaust efficiency if the exhaust port protrudes in such area. Accordingly, the exhaust efficiency can be improved at a maximum by having the exhaust port to protrude in a direction opposite to the extending direction of the support part of the placement table.
In the above-mentioned invention, the support part may have a hollow structure, and a utility supply line may be provided therein. Additionally, the utility supply line may include at least one of a gas supply line, a cooling medium supply line and a power supply line. Further, the support part may be detachably attached to the vacuum chamber.
Additionally, in the above-mentioned invention, a baffle plate may be provided so as to surround the placement stage. The baffle plate preferably has many apertures, and an open area ratio on a side to which the exhaust port is displaced may be smaller than an open area ratio on the opposite side.
Additionally, in the above-mentioned invention, a displacement of the center axis of the exhaust port with respect to the center axis of the placement stage is preferably equal to or smaller than one eleventh of a diameter of the exhaust port. The exhaust port is preferably connected to a vacuum pump having a capacity to maintain the vacuum chamber at a pressure less than 10 Pa. The vacuum pump may be a turbo-molecular pump.
Additionally, in the above-mentioned invention, it is preferable that a gas supply part constituting a substantially circular showerhead is provided in the vacuum chamber, and a center axis of the showerhead is coincident with the center axis of the placement stage.
The placement stage and the gas supply part may be configured to apply a film deposition process to the object to be processed. Additionally, an upper electrode and a lower electrode may be provided so as to face to each other, wherein plasma of a process gas is generated between the upper electrode and the lower electrode so as to apply a film deposition process to the object to be processed by the generated plasma.
There is provided according to another aspect of the present invention a vacuum processing method for applying a predetermined process to an object to be processed in a vacuum chamber, the vacuum processing method comprising: placing the object to be processed at a position above an exhaust port of the vacuum chamber, a center of the object being horizontally displaced from a center of the exhaust port by a predetermined distance; and supplying a process gas to the object to be processed from a side opposite to the exhaust port with respect to the object to be processed and exhausting the process gas through the exhaust port so as to apply the predetermined process. The predetermined process may be a film deposition process.
Other objects, features and advantages of the present invention will become more apparent from the following detailed description when read in conjunction with the accompanying drawings.